In 1983, the etiological cause of AIDS was determined to be the human immunodeficiency virus (HIV-1). In 1985, it was reported that the synthetic nucleoside 3′-azido-3′-deoxythymidine (AZT) inhibited the replication of human immunodeficiency virus. Since then, a number of other synthetic nucleosides, including 2′,3′-dideoxyinosine (DDI), 2′,3′-dideoxycytidine (DDC), 2′,3′-dideoxy-2′,3′-didehydrothymidine (D4T), ((1S,4R)-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol sulfate (ABC), cis-2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane((−)-FTC), and (−)-cis-2-hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane (3TC), have been proven to be effective against HIV-1. After cellular phosphorylation to the 5′-triphosphate by cellular kinases, these synthetic nucleosides are incorporated into a growing strand of viral DNA, causing chain termination due to the absence of the 3′-hydroxyl group. They can also inhibit the viral enzyme reverse transcriptase.
Drug-resistant variants of HIV-1 can emerge after prolonged treatment with an antiviral agent. Drug resistance most typically occurs by mutation of a gene that encodes for an enzyme used in viral replication, and most typically in the case of HIV-1, reverse transcriptase, protease, or DNA polymerase. Recently, it has been demonstrated that the efficacy of a drug against HIV-1 infection can be prolonged, augmented, or restored by administering the compound in combination or alternation with a second, and perhaps third, antiviral compound that induces a different mutation from that caused by the principle drug. Alternatively, the pharmacokinetics, biodistribution, or other parameter of the drug can be altered by such combination or alternation therapy. In general, combination therapy is typically preferred over alternation therapy because it induces multiple simultaneous pressures on the virus. However, drug resistance can still emerge, and no effective cure has yet been identified, such that a patient can ultimately stop treatment.
Treatment for AIDS using attachment and fusion inhibitors as well as other antiviral drugs has been somewhat effective. Current clinical treatments for HIV-1 infections include triple drug combinations called Highly Active Antiretroviral Therapy (“HAART”). HAART typically involves various combinations of nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, and HIV-1 protease inhibitors. In compliant patients, HAART is effective in reducing mortality and progression of HIV-1 infection to AIDS. However, these multidrug therapies do not eliminate HIV-1 and long-term treatment often results in multidrug resistance. Also, many of these drugs are highly toxic and/or require complicated dosing schedules that reduce compliance and limit efficacy. There is, therefore, a continuing need for the development of additional drugs for the prevention and treatment of HIV-1 infection and AIDS.
It would be useful to have combination therapy that minimizes the virological failure of patients taking conventional antiretroviral therapy. It would also be useful to provide a therapy that can provide a cure for HIV/AIDS, by destroying the virus altogether in all its reservoirs. The present invention provides such therapy, as well as methods of treatment using the therapy.